A VAD is a device which is used to assist the heart of a mammalian subject such as a human patient. A typical VAD includes a pump which is implanted in the body of the subject. The pump typically has an inlet connected to a source of blood to be circulated, and an outlet connected to an artery. Most typically, the inlet of the pump is connected to the interior of the left ventricle and the outlet of the pump is connected to the aorta, so that the pump operates in parallel with the left ventricle to impel blood into the aorta. The pump may be a miniature rotary impeller pump having an impeller disposed in a pump housing and driven in rotation by a small electric motor which may be closely integrated with the pump. The motor in turn typically is powered by an implantable power source such as a storage battery with an arrangement for charging the battery from an external power source. The VAD typically includes a control system which controls operation of the power source so as to drive the impeller at a set rotational speed and thus provide constant pumping action.
VADs can be used to assist the heart of subjects suffering from conditions which impair the pumping ability of the heart. Such assistance can be provided permanently, or while the subject awaits a suitable heart transplant. In other cases, the assistance provided by the VAD allows the heart to heal. A VAD may be provided to assist with pumping on either or both sides of the patient's heart. For instance, for conditions impairing the ability of the left side of the heart to pump blood into the systemic circulation, the patient may be provided with a left ventricular assist device (LVAD). For conditions impairing the ability of the right side of the heart to pump blood into the pulmonary circulation, the patient may be provided with a right ventricular assist device (RVAD). For conditions impairing both sides of the heart, the patient may be provided with a biventricular assist device (BiVAD).
In many of the above instances, the patient's condition may result in the left and right sides of the heart having disparate outputs. Because the blood output from one side of the heart is received by the other side of the heart, a disparate output between the two sides can result in an unwanted accumulation of blood at the entry to the side of the heart having the lower output. For instance, if the left side of the heart outputs less blood than the right side, blood may accumulate in the patient's lungs, and may even result in pulmonary edema (drowning).
Therefore, it is desirable to provide a method and/or system for monitoring and regulating blood output on both sides of the heart to prevent unwanted accumulations of blood in the cardiovascular system of the patient.